Electroformed microchannel cooler and methods of making same

ABSTRACT

An electroformed microchannel cooler for liquid cooling has an upper component and a lower component. Each component includes a sheet, a plurality of electroformed partition walls and a boundary wall electroformed outwardly of the plurality of partition walls. The partition and boundary walls of the upper component are attached to the boundary and partition walls of the lower part to provide a plurality of microchannels for flowing liquid through the cooler in a heat exchange relationship. One of the components has gates at each end opening into plenums inside the boundary walls. An alternate embodiment has a corrugated electroformed member attached to upper an lower sheets forming a plurality of parallel microchannels. Methods of making the electroformed microchannel coolers are also disclosed.

FIELD OF THE INVENTION

This invention relates to coolers and methods of making coolers.

BACKGROUND OF THE INVENTION

The trend in integrated circuit (IC) design, particularly in central processing units (CPUs), is increased speed and circuit density. Increased speed and circuit density causes the IC or CPU to generate more heat. This raises a need for cooling because without sufficient cooling, the IC or CPU may run slower and degrade leading to a shortened life span. Moreover, such ICs and CPUs are being used in electronic devices, such as servers and portable computers, having housings that are getting smaller and smaller which exacerbates the cooling need.

It is already known to use water or liquid cooling systems in such situations. See for instance, U.S. Pat. No. 6,674,642 B1 granted to Richard C. Chu et al. Jan. 6, 2004, disclosing a cooling system in which a heat generating electronic component 16 is cooled by a low profile cold plate 20. The cold plate 20, in turn transfers heat to liquid coolant flowing through tube 24 which is part of a heat exchange assembly 30.

See also U.S. Pat. No. 6,587,343 B2 granted to Shlomo Novotny et al. Jul. 1, 2003, disclosing a cooling system in FIGS. 6-8 in which an electronic component 88 is cooled by a cold plate 64. Cold plate 64, which typically includes tubes (not shown) through which liquid flows, is part of a heat exchange system that includes a heat exchanger 65 and a pump 66.

See also U.S. Pat. No. 6,337,794 B1 granted to Dereje Agonafer et al. Jan. 8, 2002, disclosing in FIGS. 1 and 2, a heat sink 10 having multiple channels therethrough within which liquid coolant flows. The heat sink 22 shown in FIGS. 3 and 3A has counterflow channels 22 a and 22 b with inlets 24 a and 24 b respectively and outlets 26 a and 26 b respectively. Heat Sink 20 includes an inlet plenum 30 and an outlet plenum 34 as best shown in FIG. 3A.

SUMMARY OF THE INVENTION

This invention provides a heat sink or cooler that is very compact and efficient. The cooler is characterized by a plurality of microchannels that are electroformed.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side view of a device having an electroformed micro-channel cooler in accordance with the invention;

FIG. 2 is a section taken substantially along the line 2-2 of FIG. 1 looking in the direction of the arrows and showing a top view of the manifold;

FIG. 3 is a section taken substantially along the line 3-3 of FIG. 1 looking in the direction of the arrows and showing a top view of a gated part of the two piece electroformed micro-channel cooler shown in FIG. 1;

FIG. 4 is a section taken substantially along the line 4-4 of FIG. 1 looking in the direction of the arrows and showing a bottom view of a non-gated part of the electroformed micro-channel cooler shown in FIG. 1;

FIG. 5 is a section taken substantially along the line 5-5 of FIG. 3 in the direction of the arrows and showing details of the two piece electroformed micro-channel cooler shown in FIG. 1;

FIGS. 6-9 are schematic sections similar to FIG. 5 showing a method of making the electroformed micro-channel cooler shown in FIG. 1;

FIG. 10 is a schematic section similar to FIG. 5 showing an alternate electroformed micro-channel cooler in accordance with the invention;

FIG. 11 is a plan view of a tooling plate for assembling electroformed micro-channel coolers of the invention;

FIG. 12 is a plan view of the tooling plate of FIG. 11 with a first workpiece mounted on it;

FIG. 13 is a fragmentary plan view of a second workpiece;

FIG. 14 is a plan view of the tooling plate and first workpiece of FIG. 12 with the second workpiece of FIG. 13 mounted upside down on the first work piece;

FIG. 15 is a schematic section similar to FIG. 5 showing another alternate micro-channel cooler of the invention; and

FIG. 16 is a perspective view of yet another alternate micro-channel cooler of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION

Referring now to FIGS. 1 through 4, a device 10 having an electroformed micro-channel cooler 12 in accordance with the invention is shown. Device 10 comprises a manifold 14 having an inlet 16 communicating with an inlet slot 18 and an outlet 20 communicating with an outlet slot 22. Inlet 16 feeds a heat transfer medium, such as water into cooler 12 via inlet slot 18. The cooling medium exiting cooler 12 flows out outlet 20 after being collected by outlet slot 22.

The electroformed micro-channel cooler 12 is a two-piece structure comprising a gated component 24 and a non-gated component 26. Gated component 24 comprises a thin sheet 28 which serves as a base, a generally rectangular boundary wall 30, and a plurality of partition walls 32 forming micro-channels 34 as best seen in FIGS. 3 and 5. The ends of partition walls 32 are spaced from the two shorter sides of boundary wall 30 to form an inlet plenum 36 at one end and an outlet plenum 38 at an opposite end. Sheet 28 has a first series of gates 40 providing passages from inlet slot 18 to inlet plenum 36 and a second series of gates 42 providing passages from outlet plenum 38 to outlet slot 22. Gates 40 and 42 are formed by punching holes through sheet 28. While square holes are shown, other shapes may be used. Gated component 24 is made of a material that is a good conductor of heat and electricity. Preferably, gated component 24 is made of copper which is an excellent conductor of heat and electricity.

Non-gated component 26 is substantially identical to gated component 24, the significant exception being that the base sheet 28 does not have the series of gates 40 and 42 as best shown in FIG. 4. Non-gated component 26 is placed upside down on gated component 24 so that the tops of the boundary walls 30 and the partition walls 32 are attached to each other by a suitable layer 44 of adhesive, preferably solder as best shown in FIG. 5 which is a substantial enlargement of the section taken along the line 5-5 of FIG. 3 looking in the direction of the arrows. When the gated and non-gated components 24 and 26 are attached together, the resulting cooler has a closed chamber with an inlet plenum 36 at one end fed through gates 40 in bottom sheet 28, an outlet plenum 38 at the opposite end exiting through gates 42 and a plurality of closed micro channels 34 extending from the inlet plenum 36 to the outlet plenum 38.

Referring now to FIGS. 6-9, cooler 12 is made as follows. A patterned layer of photoresist 46 is applied to the top of the thin sheet 28 of copper or the like. The photoresist has voids 48 exposing the sheet 28 where the boundary wall 30 and partition walls 32 are desired as best shown in FIG. 6. The boundary wall 30 and partition walls 32 are then electroplated onto the sheet 28 in voids 48. Voids 48 are not filled to the top, leaving room for applying a solder or other adhesive layer 44 to the tops of the boundary wall 30 and the partition walls 32 as best shown in FIG. 7. The adhesive layer 44 is then applied after which the photoresist 46 is then stripped as best shown in FIG. 8. Gates 40 and 42 are punched through sheet 28 before the photoresist 46 is applied or after the photoresist is stripped to provide the gated component 24 as best shown in FIGS. 8 and 9. The non-gated component 26 is made in the same way except that gates 40 and 42 are not punched through sheet 28 as best shown in FIG. 9.

The non-gated component 26 is then turned upside down and placed on the gated component 24 with the layers 44 of solder on the respective tops of the boundary walls and the partition walls engaging each other as shown in FIG. 9, or vice-versa. The layers 44 of solder are then reflowed to attach components 24 and 26 together to form the micro-channel cooler 12. Using such a technique it is possible to provide a very efficient cooler that is about 1 inch square and 0.012 inch tall with copper sheets about 0.002 inches thick, walls about 0.004 inches thick and the channels about 0.008 inches wide and tall. Such a cooler we found to have a heat transfer coefficient of about 1.5 W/cmcm/degree Centigrade.

FIG. 10 shows an alternate micro-channel cooler 112 comprising several gated components 24 and one non-gated component 26 in a stacked arrangement. In this particular arrangement there are six layers with gated component 24 a serving as the base. Gated component 24 a is attached to an upside down gated component 24 b which in turn is attached to another upside down gated component 24 c. Gated component 24 c is attached to a third upside down gated component 24 d which in turn is attached to another upside down gated component 24 e. Gated component 24 e is attached to an upside down non-gated component 26 a. It should be understood that the number of stacked arrangements is virtually unlimited so long as the first layer is a gated component and the last layer is a non-gated component and upside down with respect to the base layer, or vice-versa. With such an arrangement any number of intermediate gated and/or non-gated components can be used, right side up or upside down depending on the flow patterns and manifolding desired.

The gated and non-gated components 24 and 26 can be made singly or in gangs. When the components 24 and 26 are made in gangs, the components 24 and 26 can be assembled as explained below.

Referring now to FIG. 11, a tooling plate 50 for assembling a gangs of the components of the electroformed multichannel cooler of the invention is shown. Tooling plate 50 has a flat surface 52 and four alignment pins 54 that protrude upwardly from flat surface 52 in a rectangular array. FIG. 12 is a plan view of tooling plate 50 with a first work-piece 56 mounted on it. Work-piece 56 comprises a flat sheet 58 having four alignment holes 59 that receive the respective four alignment pins 54. Sheet 58 is stamped with several slots 60 that outline eight base plates 62 of cooler components. Each corner of each base plate 62 is attached to corners of other base plates 62 and/or to the remainder of the sheet 58 by a round connector 64. Before being assembled to tooling 50, work-piece 56 is processed as described above so that each base plate 62 is part of a non-gated component such as component 26 shown in FIG. 4.

FIG. 13 is a fragmentary plan view of a second work-piece 66. Work-piece 66 also comprises a flat sheet 68 having four alignment holes 69 for receiving respective four alignment pins 54 of tooling plate 50. Sheet 68 is also stamped with several slots 70 that outline eight base plates 72. Each corner of each base plate 72 is attached to corners of other base plates 72 and/or to the remainder of sheet 68 by a round connector 74. Work-piece 66 is processed as described above so that each base plate 72 is part of a gated component such as component 24 shown in FIG. 2. The second work-piece 66 is then mounted upside down on first work-piece 56 with alignment pins 54 protruding through alignment holes 69 as shown in FIG. 14. If two layer electroformed multichannel coolers, such as the cooler 12 shown in FIGS. 1-9 are desired, the work-pieces 56 and 66 stacked on the tooling plate 200 are simply heated to reflow the solder so that the two work-pieces are attached to each other to form several two layer coolers. The individual coolers are then separated from each other and the remainder of sheets 58 and 68 by removing the attached work-pieces and punching out the round connectors 64 and 74.

On the other hand if multi-layer electroformed multichannel coolers, such as the cooler 112 shown in FIG. 10, are desired, additional work-pieces, such as work-piece 66 are simply stacked upside down on the tooling plate 50 until the desired number of layers is reached. The stacked work-pieces are then heated to reflow the solder so that the stacked work-pieces are attached to each other to form several multi-layer coolers. The individual coolers are then separated from each other and the remainder of sheets 58 and 68 by removing the attached work-pieces and punching out round connectors 64 and 74.

FIG. 15 is a schematic section similar to FIG. 5 showing another alternate arrangement of a micro-channel cooler 212 in accordance with the invention. Cooler 212 comprises a corrugated skin 214 that is electroplated onto a corrugated mandrel (not shown). Skin 214 is removed from the mandrel and placed between two parallel sheets 216 and 218. Skin 214 is attached to sheets 216 and 218 by sheets reflowing solder layers 219 to form a plurality of parallel micro-channels 220 in cooperation with sheet 216 and a plurality of parallel channels 222 in cooperation with sheet 218. Channels 220 and 222 alternate.

Plenums are formed at the opposite longitudinal ends of channels 220 and 222 and either sheet 216 or 218 is punched to provide gates opening into the plenums.

FIG. 16 is a perspective view of yet another alternate arrangement of a micro-channel cooler 312. Cooler 312 comprises two components—a gated component 314 and a non-gated component (not shown). Gated component 314 comprises a thin sheet 316 which serves as a base, a generally rectangular boundary wall 318 and a plurality of partition walls 320 forming micro-channels 322. The micro-channels 322 radiate from a central inlet plenum 324 to a peripheral outlet plenum 326. Inlet plenum 324 has a gate 328 that provides an inlet into plenum 324. Outlet plenum 326 has a plurality of gates 330 that provide outlets for plenum 326. Gates 328 and 330 are provided by punching holes through sheet 316. While round holes are shown, other shapes may be used.

Gated component 314 is made in the same way as gated component 24 by electroplating boundary and partition walls 318 and 320 in the voids of a photoresist pattern on the top of sheet 316 and then applying a solder or other adhesive to the tops of the walls. The photoresist is then stripped away. Gates 328 and 330 are punched through sheet 316 before or after the photoresist is stripped away.

A non-gated component (not shown) is made in the same way except that gates are not punched through base sheet 316. The non-gated component is turned upside down and attached to gated component 314 by reflowing the solder or activating the adhesive to provide the micro-channel cooler 312. Cooler 312 can be made with just two components as in the case of cooler 12 or with several components as in the case of cooler 112.

Many embodiments and adaptations of the present invention other than those described above, as well as many variations, modifications and equivalent arrangements, will be apparent from or reasonably suggested by the present invention and the foregoing description, without departing from the substance or scope of the present invention. Accordingly, while the present invention has been described herein in detail in relation to preferred embodiments, it is to be understood that this disclosure is only illustrative and exemplary of the present invention and is made merely for purposes of providing a full and enabling disclosure of the invention. The foregoing disclosure is not intended or to be construed to limit the present invention or otherwise to exclude any such other embodiments, adaptations, variations, modifications and equivalent arrangements, the present invention being limited only by the following claims and the equivalents thereof. 

1. An electroformed microchannel cooler for liquid cooling comprising: an upper sheet a lower sheet and a plurality of electroformed partition walls disposed between the upper sheet and the lower sheet to provide a plurality of microchannels for flowing liquid through the cooler.
 2. An electroformed microchannel cooler for liquid cooling comprising: an upper component and a lower component, each component comprising a sheet and a plurality of electroformed partition walls, the partition walls of the upper part engaging the partition walls of the lower part to provide a plurality of microchannels for flowing liquid through the cooler in a heat exchange relationship.
 3. The electroformed microchannel cooler as defined in claim 2 wherein the partition walls of each component have ends engaging the ends of the other component.
 4. The electroformed microchannel cooler as defined in claim 3 wherein the ends of the partition walls of one component are soldered to the partition walls of the other component.
 5. The electroformed microchannel cooler as defined in claim 3 wherein each component has a boundary wall outwardly of the plurality of partition walls forming plenums at each end of the cooler and wherein one of the components has gates at each and opening into the plenums.
 6. The electroformed microchannel cooler as defined in claim 5 wherein the components are made of copper.
 7. The electroformed microchannel cooler as defined in claim 6 wherein the sheets have a thickness of about 0.002 inches, the boundary and partition walls have a thickness of about 0.004 inches, and the microchannels are about 0.008 inches wide and 0.008 inches tall.
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 16. A microchannel cooler for liquid cooling comprising: an upper component and a lower component, each component comprising a sheet and a plurality of partition walls, the partition walls of the upper part engaging the partition walls of the lower part to provide a plurality of microchannels for flowing liquid through the cooler in a heat exchange relationship, the plurality of partition walls of each component having ends engaging the ends of the plurality of partition walls of the other component.
 17. The microchannel cooler as defined in claim 16 wherein the ends of the partition walls of one component are attached to the ends of the partition walls of the other component.
 18. The microchannel cooler as defined in claim 16 wherein the ends of the partition walls of one component are soldered to the ends of the partition walls of the other component.
 19. The microchannel cooler as defined in claim 16 wherein each component has a boundary wall outwardly of the plurality of partition walls forming plenums at each end of the cooler and wherein one of the components has gates at each end opening into the plenums.
 20. The microchannel cooler as defined in claim 19 wherein the components are made of copper.
 21. The microchannel cooler as defined in claim 19 wherein the sheets have a thickness of about 0.002 inches, the boundary and partition walls have a thickness of about 0.004 inches, and the microchannels are about 0.008 inches wide and 0.008 inches tall.
 22. A microchannel cooler for liquid cooling comprising: an upper component and a lower component, each component comprising a sheet and a plurality of partition walls, the partition walls of the upper part engaging the partition walls of the lower part to provide a plurality of microchannels for flowing liquid through the cooler in a heat exchange relationship, the plurality of partition walls of each component having ends attached to the ends of the plurality of partition walls of the other component, each component having a boundary wall outwardly of the plurality of partition walls forming plenums at each end of the cooler, and one of the components having gates at each end opening into the plenums.
 23. The microchannel cooler as defined in claim 22 wherein the components are made of copper.
 24. The microchannel cooler as defined in claim 22 wherein the sheets have a thickness of about 0.002 inches, the boundary and partition walls have a thickness of about 0.004 inches, and the microchannels are about 0.008 inches wide and 0.008 inches tall. 